Ceramic thermal spray coatings are used in various applications according to the properties of the constituent ceramics. For example, aluminum oxide thermal spray coatings are used as protective coatings for various members because aluminum oxide exhibits high electric insulation, abrasion resistance, and corrosion resistance. Yttrium oxide thermal spray coatings are used as protective coatings for members in semiconductor device production apparatuses because yttrium oxide exhibits high plasma erosion resistance (see, for example, patent document 1 and patent document 2).
A ceramic thermal spray coating can be formed by thermally spraying a slurry containing ceramic particles (see, for example, patent document 3). However, during the storage of the slurry, the ceramic particles in the slurry are sedimented by gravity and thus precipitates of the ceramic particles are sometimes produced. The precipitated ceramic particles are required to be redispersed before the thermal spraying of the slurry, and hence a slurry tending to produce precipitates is likely to be regarded as unsuitable for practical applications.